Seat belt retractor with electric motor

Abstract

A retractor for a seat belt of a vehicle has a winding shaft for winding up a seat belt. A motive spring biases the winding shaft in the winding direction of the seat belt. An electric motor produces torque can be transmitted to the motive spring to change the spring force. A switch coupling transmits the torque of the electric motor to the winding shaft to wind up the seat belt. A gear transmits the torque of the electric motor to the winding shaft or the motive spring. The motive spring, the coupling and the gear are provided on one side of the seat belt retractor. The gear comprises a drive wheel which is rotatably mounted on a shaft rotationally and coaxially connected to a winding shaft, and which is rotationally connected to an outer spring end of the motive spring by a rigid rotary connection. A first active surface of the coupling is movably mounted against a restoring force on a component securely connected to the rigid rotary connection and is able to rotate around the shaft. A second active surface of the coupling is rotationally connected to the shaft.

1 . A seat belt retractor comprising a winding shaft for winding up a seat belt, a motive spring to bias the winding shaft in the winding direction of the seat belt, an electric motor from which a torque can be transmitted to the motive spring to change the spring force, and a switch coupling, via which the torque of the electric motor can be transmitted to the winding shaft to wind up the seat belt, and a gear to transmit the torque of the electric motor to the winding shaft or the motive spring, whereby the motive spring, the coupling and the gear are provided on one side of the seat belt retractor, the gear comprises a drive wheel which is rotatably mounted on a shaft rotationally and coaxially connected to a winding shaft, and which is rotationally connected to an outer spring end of the motive spring by a rigid rotary connection and a first active surface of the coupling is movably mounted against a restoring force on a component securely connected to the rigid rotary connection and able to rotate around the shaft and a second active surface of the coupling is rotationally connected to the shaft.  
     
     
         2 . The seat belt retractor according to  claim 1 , wherein the first active surface of the coupling can be moved into the engaged position with the second active surface by an electrical signal or by an inertial force.  
     
     
         3 . The seat belt retractor according to  claim 1 , wherein the electric motor, the motive spring and the coupling are a unit which can be mounted to the shaft.  
     
     
         4 . The seat belt retractor according to  claim 2 , wherein the electric motor, the motive spring and the coupling are a unit which can be mounted to the shaft.  
     
     
         5 . The seat belt retractor according to  claim 1 , wherein the gear is a toothed gear system.  
     
     
         6 . The seat belt retractor according to  claim 1 , wherein the gear is a screw gear.  
     
     
         7 . The seat belt retractor according to  claim 1 , wherein the gear, the coupling and the motive spring are arranged on the side of the seat belt retractor on which the vehicle and belt webbing sensitive sensor device are provided.  
     
     
         8 . The seat belt retractor according to  claim 7 , wherein on the other side of the seat belt retractor, a pyrotechnically driven tightening device is arranged, which drives the winding shaft in the winding direction for the power tightening of the seat belt.  
     
     
         9 . The seat belt retractor according to  claim 1 , wherein the operation of the electric motor is activated by a pre-crash sensor signal and the operation of the pyrotechnically driven tightening device is activated by a crash sensor signal.  
     
     
         10 . The seat belt retractor according to  claim 1 , wherein the electric motor and the pyrotechnically driven tightening device are secured to a common seat belt retractor frame.  
     
     
         11 . The seat belt retractor according to  claim 9 , wherein the unit comprising the gear, the coupling and the motive spring is also secured to a common seat belt retractor frame.